Here are some in game screenshots of the Golden Guns.  Golden Guns are achieved by completing Expert Level 3 in every gun per class.  Expert Level 3 is achieved by getting (usually) 150 Headshots per gun.

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Golden AK-47 Assault Rifle

Golden Mini-Uzi SMG

Golden M60E4 LMG

Golden M1014 Shotgun

Golden Dragunov Sniper Rifle

And Finally the Desert Eagle, you get for getting to Rank Level 55

Golden Desert Eagle Sidearm

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